The subject line pretty much says it all. After I shutdown my computer and I go to turn it on again maybe 12 hours later, the fan will spin and the HDD light will come on, but no POST. I have to switch off the PSU (switch in the back) and turn it back on before it will POST and boot properly. I have tried replacing the PSU and that does not appear to be the problem.

Any ideas?

No ideas until we get more information.

Tell us everything about your system. Then someone might be able to help you.

^ Yeah full specs please.

include:
CPU
GPU
Motherboard
RAM
HDD
PSU
and anything connected

When did the porblem start happening?
Does the computer run stable when it is on?
Post your operating temperatures as well please.

MB: Asus P5K-Deluxe/WiFi
GPU: EVGA 8800GTS 320mb
RAM: 4gigs (2gigs ocz, 2gigs crucial)
HDD: Western Digital 160gb
PSU: Antec Truepower Trio 650W
CPU: Core 2 Duo E6850

Connected items: wifi antenna, speaker, monitor

Problem started happening pretty much immediately after I built the computer. Computer runs stable when it is on (although Age of Conan is crashing - but I think that is due to the game itself)

I don't have operating temp of the CPU. GPU is running about 54-75 depending on if I'm playing a game or not.

My monitor seems to be a little faulty - it only occasionally detects a signal. I sometimes have to reboot to get the monitor to show anything. Sometimes it won't get a signal until windows loads up. Kind of random. Could this have anything to do with it?

Much better...
Do you happen to know what model of RAM you have (for both)?

It does seem weird that the computer doesn't turn on after hours of being off.

Do you run any other graphic intensive games?
Is there any artifacting occuring whilst running (weird pixels, distored models)?

That last monitor problem seems to indicate a graphics card problem... but AFAIK those problems tend to be persistant, the whole card not working rather than occassionally.

What case do you use?

Have you installed all the drivers for your machine?

Does your computer turn on immediately after turning it off?

Thanks for the response.

I will have to look into the memory model #s when I get home tonight.

Nope, no other problems with other games. The next most graphically intensive game would probably be WoW, which does not crash (black screen/lock up).

I had the same monitor issue (same monitor) with an old computer I previously built - so I'm leaning toward it being the monitor. I used a previous monitor I had and it would pick up a signal everytime.

Case is the sonata III by antec.

Yes, computer turns on immediately after turning it off (at least it will POST). Again, sometimes the monitor will not pick up a signal and will have to reboot anyways.

One side note (may be unrelated): When I have crashed in AoC, I will sometimes get an error during bootup that says Overclocking failed and give me options to change settings in the bios or to use default settings. As far as I know, the only thing that might be overlocked in the GPU and that is factory overclocked.